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net_sched: introduce tracepoint trace_qdisc_enqueue()

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Tracepoint trace_qdisc_enqueue() is introduced to trace skb at
the entrance of TC layer on TX side. This is similar to
trace_qdisc_dequeue():

1. For both we only trace successful cases. The failure cases
   can be traced via trace_kfree_skb().

2. They are called at entrance or exit of TC layer, not for each
   ->enqueue() or ->dequeue(). This is intentional, because
   we want to make trace_qdisc_enqueue() symmetric to
   trace_qdisc_dequeue(), which is easier to use.

The return value of qdisc_enqueue() is not interesting here,
we have Qdisc's drop packets in ->dequeue(), it is impossible to
trace them even if we have the return value, the only way to trace
them is tracing kfree_skb().

We only add information we need to trace ring buffer. If any other
information is needed, it is easy to extend it without breaking ABI,
see commit 3dd344ea84 ("net: tracepoint: exposing sk_family in all
tcp:tracepoints").

Reviewed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Qitao Xu <qitao.xu@bytedance.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Qitao Xu
2021-07-14 23:03:24 -07:00
committed by David S. Miller
parent 851f36e409
commit 70713dddf3
2 changed files with 42 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
net/core/dev.c
View File

@@ -131,6 +131,7 @@
#include <trace/events/napi.h>
#include <trace/events/net.h>
#include <trace/events/skb.h>
#include <trace/events/qdisc.h>
#include <linux/inetdevice.h>
#include <linux/cpu_rmap.h>
#include <linux/static_key.h>
@@ -3844,6 +3845,18 @@ static void qdisc_pkt_len_init(struct sk_buff *skb)
}
}
static int dev_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *q,
struct sk_buff **to_free,
struct netdev_queue *txq)
{
int rc;
rc = q->enqueue(skb, q, to_free) & NET_XMIT_MASK;
if (rc == NET_XMIT_SUCCESS)
trace_qdisc_enqueue(q, txq, skb);
return rc;
}
static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
struct net_device *dev,
struct netdev_queue *txq)
@@ -3862,8 +3875,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
* of q->seqlock to protect from racing with requeuing.
*/
if (unlikely(!nolock_qdisc_is_empty(q))) {
rc = q->enqueue(skb, q, &to_free) &
NET_XMIT_MASK;
rc = dev_qdisc_enqueue(skb, q, &to_free, txq);
__qdisc_run(q);
qdisc_run_end(q);
@@ -3879,7 +3891,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
return NET_XMIT_SUCCESS;
}
rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;
rc = dev_qdisc_enqueue(skb, q, &to_free, txq);
qdisc_run(q);
no_lock_out:
@@ -3923,7 +3935,7 @@ no_lock_out:
qdisc_run_end(q);
rc = NET_XMIT_SUCCESS;
} else {
rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;
rc = dev_qdisc_enqueue(skb, q, &to_free, txq);
if (qdisc_run_begin(q)) {
if (unlikely(contended)) {
spin_unlock(&q->busylock);